Apparatus for forming grinding wheels



Sept. H4, 1,948. D. E. MULHOLLAND 2,449,407A APPARATUS FOR FORMING GRINDING WHEELS Filed May 2,4, 1943 f s sheets-sheet 1 Sept M 1948. D. E. MULHOLLAND 2,449,407

APRARATUS FOR FORMING GRINDING WHEELS Filed May 24, 1945 -s sheets-sheet 2 -Sept 141, 1948.. D. E. MULHOLLAND 2,449,497

u APPARATUS FOR FORMING GRINDING WHEELS .75 Sheets-Sheet 3 Filed May 24, 1945 Patented Sept. 14, 1948 APPARATUS FOR FORMING ('irRIND-Iltl'Gr` WHEELS d David' E. Mulholland, Fort Myers, Fla., assigner to Walter S.= Mulholland, Reading, Pa.

Application May 24, 1943, Serial No. 488,255

My invention relates to' an apparatus for forining wheels for grinding or polishing lenses, quartz, prisms and other articles made of glass, metal or the like.V

The principal object of the' invention ls to provide a grinding or polishing wheel with a portion containing abrasive or polishing material which is of substantially uniform density, the voids being substantially uniformly distributed throughoutV the mass so that all portions of the grinding or polishing area thereof will wear at` the same rate. o

A primary featurel of theV invention consists' in placing an uncompacted mixture of abrasive grains or polishing material and a bonding medium into a mold; applying fluid pressure to the mixture andl subsequently applying heat to the mold while the pressure ismaintained to either chemically change the bond orto solidify the same.

Another'feature4 of the invention consists' in providing a mold for receiving' the mixture containing abrasive or polishing material, the mold having a substantially cylindrical side wall and a removable top wall anda uid pressure ac tuated deformable means within the mold for cooperating with the mixturel placed therein whereby the latter is subjected to uniform Huid pressure for compressing it tov substantially uniform density.

A further featurey of theinvention consists in providing the mold for receiving a mixture con-l taining abrasive or polishing material with resilient and exible means subject to fluid pressure adapted to encircleV the mixture within the mold, said means being adapted to transmit pressure radially to the mixture for compressing it to substantially uniform density.I

A still further feature of the invention consists in providing a mold having a base and a cylindrical side wall and in having `a wheel hub disposed within the mold which denes with the side wall thereof an annular space for `receiving a mixture of abrasive or pol-ishingmaterial, fluid pressure operated'means being provided for compressing the mixture in the mold to substantially uniform density.

Other and more specilic features of the invention, residing in advantageous forms,V combinations'and relations of parts, will hereinafter appear and be pointed out in thev claims. Y

In the drawings,

Figure 1 is a view partially in plan and partially in section of one embodiment of the apparatus `used in constructing the abrasive or polishingwheel.

Claims. (Cl. 18-5)` Figure 2 is a sectional view taken on line 2,--2`

of Figure 1.

`Figure 3 is a viewsimlar to Figure 1 illustra-tf!-` ing amodied form of the invention.

Figure 4 is a sectional view taken on line 4--4 of Figure 3.

Figure 5 is a plan view of still another modied form of the invention.

Figure 6 is a sectional view taken on line 6-6` of Figure 5.

Referring more particularly to the drawings,

and especially to the form of the invention shown inv Figures 1 and 2 thereof, I indicates the mold or die having a base 2 and a cylindrical side wall 3 which is preferably formed as a separate ring-shaped member and is removably secured to the base by a plurality of bolts 4 whose heads are countersunk in recesses 5` in the under side of the base 2; l

The side wall 3 is advantageously provided with an upper removable ring section or member 6 and these twoparts are rigidly secured together by a plurality of bolts 'I whose heads may be conveniently countersunk in recesses 8 in the upper surface of the ring 6.

Overlapping the inner face of the cylindrical side wall 3 is a iiexible and resilient diaphragm 9 which is made of any suitable material which will readily yield in response to fluid pressure, This ring-shaped diaphragm has outwardly extending portions I and II respectively adjacent its upper and lower edges. The upper portion or flange It of the diaphragm isrmly clamped between ring 6 and the side wall 3 of the mold while the bottom portion or iiangel II is `iirrnly clamped between the side wall and the base of the mold. The diaphragmand its anges are, of course, continuous and the faces of the base `2, side wallgtand ring 6 which coact to clamp the diaphragm are suitably roughened or serrated, as indicated at I2, so that, when the bolts# and l are tightened, the diaphragm is sealed with respect to the side wall 3. d j

Extending completely through the sidewall 3V from the outer side `thereof to the inner face of 'the diaphragm is a passageway I3 which is the centering member `in place.- I l Member I5 serves to center within the mold a wheel slipping with respect to the shaft and with.

an entire absence of lateral play in the Wheel so long as the coacting inclined surfaces of the sub and shaft are maintained inY engagement. The outer surface of the centering member I5 is conically tapered to exactly the same degree as the inner surface of the hub so that the hub will always be accurately centered V,within there mold. .Y

The hub employed preferably has swedged on its outer surface a band or ring whose inner surface is conveniently formed with marginal flanges 2I and22, the inner surfaces of which engage the outer face of the hub I9. This band`26 permits the grinding or polishing portion of the wheel to be readily replaced after the same has worn to itsrpermlssive limit. Thehub member and the side wall of the mol-d on which the diaphragm 9 ris mounted define an annular space for receiving a mixture, designated 23, of anl abrasive or p-olishingmaterial and a -sui-table bonding medium such as shel'lac, crude rubber or synthetic resin. While the mixture may be of any desired consistency whenfintroduced in the mold, I have found that with-either shellac or a resin bond the best results are obtained when it is in a granular state. In the initial forming of a rubber bonded abrasive or polishing material the crude rubber or latexis intimatrely-mixed with the `abrasive gr-ains or the .polishing powder and with the vulcanizing material by rubber mills or the like and th-e resultant product stripped from theserolls may be used if desired-toflll the space 23 of the mold.

.Y When the space between the hub and the side wall ofthe moldhas been filled with the mixture of abrasive or polishing material and bonding me- Y vsion and contraction of the mass during the heatg 4 mass will be greatly reduced in area and theV density of the mass will be substantially uniform over its entire cross sectional area.

While still under pressure, the mixture is heated to a temperature suflicient to cure the bonding medium of the mixture. The heating may be conveniently accomplished by placing the entire mold in a suitable heating. chamber. The pressure on the abrasive mixture should be maintained substantially constant and suitable means (no-t shown) is provided to compensate for the expaning and cooling cycles to which the mass is subjected as' will be later pointed out. After the bonding medium has hardened, set or cured, the heating chamber is opened and after th-e mold has cooled the pressure is released, the mold withdrawn from the chamber and the cover 2t is then removed and the grinding or polishing wheel taken from themold. It will, of course, be appreciatedthat thefouter surface of the abrasive .por-

tion ofl the wheel will not be entirely smooth or it might not even be concentric with. the. axis of the wheel.` Consequently it may be necessary to millor grindl thel outersurface of the Wheel until it is concentric with itsaxis and to thev desired degree of smoothness.

Agrinding or polishiagvinei when formed by density throughout its entire cross sectional area-.iV

Not `only are the voids of small size but theyseem to be uniformly distributed throughout `the mass.

- Since theentire operation'is performed with both thernold and the grinding orpolishing material in a static condition the uniform distribution-of the abrasive grain' or the polishing material whichV was obtained priorto the entry of @the mass within the mold is not disturbed and the abrasive grains d'ium to approximately the top of the hub, the

mold is jclosed by a top wall or cover 24, which is afdpted to seat on top ofthe centering' member [5v-and the `hub and` also to neatly fit withinthe inner face of the upper portion of the diaphragm 9. lThe top wall may be conveniently secured-in place by means of a stud 25 which extends through an :opening in the center `thereof and is screw threaded with the centering member I5. The upper end' of the stud `2.5 4is provided with a transverse slot for receiving a wedge-shaped key 2-5 which ls, adapted to engage the outer-'face of the top wall 24 and thereby easily and effectively secure it in place. Y Y

/ With the top wall V2li thus secured in place,

fluid under predetermined pressure is admitted to the passageway I3 and is thus applied to the inner face of the diaphragm, not only at the point adjacent the inner end of the passageway but` to the entire inner face of the diaphragm because the latter Vflexes easily and permits the uid under pressure to readily pass between th-e contiguous faces of the diaphragm and side wan s ofthe mold. Due to the flexibility and resiliency of the diaphragm, the mixture of abrasive or polishing material and bonding medium within the mold will becompressed to substantially uniform density; The pressure on the mixture being radially inward andgbeing uniform throughout the entire dia-- phragm since the fluid is static or'substantially so a-t the time the opti'llllimfpressureA is maintained, henceV any large voids Vif presentin :the

thedesir-edcharacter whichafter being trued will` be found i-tobe substantially in balance-:not only initially but `throughout the life ofth'egrinding orU polishing portion tl'ereof;A

In the form of the invention ures -3-and 4, themoldlisprovided with the same principal 4partsas the one shown in Figures :land

2; namely,l a'base 36 cylindrical side ,wall 3 I ,-'t op ring 32', "flexible diaphragm 33,*avr centering 'member 3 4f-andcover 35,.v The only changeinY the bodiment of the invention shown inllligures- 3.v andll'is that a ring 361s loosely-mountedfbetween the cylindrical sidewall .3 I Vof the] moldand "the flexible diaphragm 3. The ring 35 is rprovdedwith a plurality of radial openings ilwhich` communi- One of, these circumferential grooves may-belocated substantially midway between thevends of.,

the side4 wall' andAV may bel semi-cylindricalin shape, while others of the grooves may be-.located adjacent the ends of the side wall; Connectingthe circumferential grooves at a pluralityof point-s at lapproximately intervals,V for -exarnple, are fa.- plurality ofl axiallyV extending semi-,circular grooves 39, ,one of which communicates with aradial passageway 40 extending-through the side musas in as."

5.. ly ows through the circumferential 'and'axial grooves 38 "and 39 respectively and thence into the radial openings 31 in the ring 36 where it coacts with the flexible diaphragm 33 to radially compress the mixture 42 of abrasive material and bonding medium on the hub 43. The method to be followed in forming .the abrasive or polishing wheel in the apparatus shown in Figures 3 and l` is the same as with the apparatus illustrated in Figures 1 and 2.

In Figures -and 6 an embodiment of the invention is illustrated for forming an abrasive disk -or polishing-wheel which is adapted to be used either for rough edge grinding or for lap grinding; that is to say, .the wheel may be mounted so that its outer curved face or periphery constitutes the working surface or so that one of its opposed fiat faces constitutes the working surface.

The mold or die illustrated in Figures 3 and 6 is of substantially cylindrical shape having a base 5U and a side wal1 5l. `The mold is closed by a cup-shaped -follower or cover 52 having an upturned peripheral flange 53 contiguous with the side wall of the mold. The follower may be advantageously held in place by a keeper member 54 which may be of substantially cruciform shape to provide a plurality of arms 55. Each of these arms has a downwardly extending portion 55 which terminates in an inturned flange 51 for projecting lbeneath the outwardly projecting annular flange 58 formed at the top of the side wall of the mold. Flange 58 has a plurality of cutout portions 59 of slightly greater width than the arms 46 so that, by initially positioning the keeper 54 with the arms 55 adjacent the cut-out portions 59, the keeper may be rotated one way or the other to bring the inturned flanges 51 of the arms into cooperative engagement with the under side of the outturned flange 58 of the mold. The keeper may be advantageously reinforced by flanges 60 extending longitudinally of the arms 55.

A iiexible and deformable diaphragm member 6I is adapted to fit within the mold between the follower 52 and the mixture 32 of abrasive or polishing material and bonding medium which is placed within the mold. Connected with the diaphragm and extending upwardly therefrom through central openings in the follower 52 and in the keeper 54 is a pipe or stem 63 communieating with the interior of the diaphragm through which fluid under pressure may be admitted thereto. As in the previously described modifications suitable means (not shown) is connected to the pipe 63 so as to maintain the fiuid under substantially uniform pressure within the flexible diaphragm during the curing and subsequent cooling of the abrasive or polishing wheel.

Fitting within a centrally located aperture in the base 56 of the mold is a cylindrical plug 64 which projects inwardly into the mold and is adapted to receive a cylindrical cup-shaped sleeve 55. This plug and sleeve is positioned within the mold before the mixture of abrasive or polishing material and bonding medium is introduced therein so that the disk will be formed with the cylindrical plug 64 molded therein. The method of forming the wheel is substantially the same as that followed with the molds illustrated in the other figures of the drawings; that is to say, the desired quantity of the mixture of abrasive or polishing material and bonding medium is placed within the mold after the sleeve 65 has been mounted therein on the plug 64. Thereafter the fiexible diaphragm which may conveniently be in the form of a rubber bag is placed on top of the mixture and the follower 52 secured in' place on top of the bag bythe keeper 54.` Fluid under pressure is then'admitted to the bag so as to compress the mixture to substantially uniform. density. While the pressure is maintained with-A inthe bag, the mold is subjected to heat to set and harden the bonding medium, after which the mold is allowed to cool and the pressure is released from thediaphragm. The mold is then opened and the wheel/removed.

If the wheel is to be used'for lap grinding, the sleeve 65 may be interiorly threadedso that the wheel may be removably` attached to a rotatable spindle and a hole may be drilled through the center'of thewheell to permit asuitable coolant to be projected through thewheel on to the work. If the wheelisto be used for edge grinding, a large opening may be bored, through the center so that it maybe easily clamped on to the end of a rotating spindle or a hub such as shown inFigures l to 4 may be substituted for` the sleeve 64. The opening for the stud I6 as shown in Figures 2 and 4 being either lled or omitted entirely.

Since the method ofmaking and the form of the wheel is identical whether polishing material, such as rouge or oxides of lead or tin, are mixed withl a bonding medium to` form a polishing wheel, or whether abrasive material, such as aluminum oxides, silica oxidesor silica carbide, are mixed with the bond, toform an abrasive wheel, the terms abrasive material and polishing ma terial, and grinding wheel, and polishing wheel. are to be considered assynonymous in the specification and appended claims.

For a number of years, there has been a controversyin the glass grinding and polishing art as to whether the polishing step is, in fact, an abrasive action or the result of a quasi-chemical reaction between the polishing medium, the coolant and the body to be polished. This controversy has not yet been definitely settled and, for this reason,if for no other, the terms abrasive and polishing used in the specification and claims should be considered as synonymous.

What I claim is:

1. An apparatus for forming a grinding wheel involving a `mold having a disc-like cavity for receiving a mixture containing abrasive material; said mold comprising a base having an upstanding frusta-conical member rigid therewith and adapted to center a hub of said wheel within said cavity, a circular side wall of uniform diameter coaxial with and spaced from said frustoconical member, means firmly securing said side wall to said base, a ring firmly secured to said side wall, an elastic lining embracing the inner area of said side wall and being clamped between said base, and ring at opposite ends of said wall, and a cover bearing upon and being removably secured to said frusto-conical member; said cover fitting neatly within said ring.

2. An apparatus for forming a grinding wheel involving a mold having a disc-like cavity for receiving a mixture containing abrasive material; said mold comprising a base having an upstanding frusto-conical member rigid therewith and adapted to center the hub of said wheel Within said cavity, a circular shallow side wall of uniform diameter coaxial with and spaced from said frusta-conical member, means firmly securing said side wall to said base, a ring mounted upon and firmly secured to said side wall, said ring being coaxial with said frusto-conical member, an elastic lining embracing the inner area.A

gaaanz:

of xsaidl. side wall: .and being- .clamped :between I adjacent I portions of said-iside wall, said. base and ring,-said elastic lining being. selectively sub-v jected to fluid pressure and adaptedto transmit saidipressure tosaid abrasive ,material for `compressing the latter against said hub tosubstantially uniform density, Vand a Vcoverco-,axialvvith said ringand adaptedto twithin the same one face of .said cover bearingfupon'and being re-V movably secured to;saidfrusto-conicahmember. f 3. In Y an .,apparatusv'for Vforming-,a v'grinding wheelinvolving a mold having a disc-likev cavity for receiving a mixture containing abrasive ma'- terial, saidmold comprising a base having a centering member rigid therewith and adapted to center the hub of said Wheel within said cavity, said base defining one side of said cavity, a circular side wall coaxial with and spaced from said centering member, means iirmly securing said side wall to said base, a ring firmly secured to said side wall'and being concentric with said centering member, an elastic liner embracing the inner area of said side Wall and being clamped by said base, side wall and ring, said elastic liner defining the 'periphery of said cavity, and a cover bearing upon and being removably secured to said centering member within said ring; said cover defining another side of said cavity. t

4. An apparatus for forming a grinding Wheel involving a Vmold having. a disc-like cavity for receiving a mixture containing abrasive material; said mold comprising a base having an upstanding frusto-conicalmember rigid therewith and adapted to center a hub of said wheel .Within said cavity, a circular side `Wall coaxial with and spaced from said frusta-conical member,'means rmly securing said side wall to said base, a ring mounted upon and rmly secured to said side wall, an elastic liner embracing the inner area of said side wall and having one edge clamped between said ring and side wall and another edge clamped between said base and side Wall, means upstanding from said frusto-conical member, a

cover bearing upon.saidfrusto-conical member within said ring, andmeans .removablysecuring said cover to said upstanding means. Y

5. An apparatus for forming a grinding wheel involving a mold having a disc-like .cavity for receiving a mixture containing abrasiveimaterial; said mold comprising a base having an upstanding frusta-conical member rigid therewith and adapted to center the hub of said wheel within said cavity, a circular side wall coaxial with and spaced from said frusto-conicalmember, means iirmly securing said side Wall to said base, a ring mounted upon and firmly secured to said side wall, an elastic liner embracing an inner' REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENT Number Name Date 224,433 Hipkins, J1'.v Feb. V10, 1880 913,057 Sa'ckett 1 Feb. 23, 1909 1,642,989 Busch Sept. 20, 1927 1,884,529 Bemmer et al Oct. 25, 1932 1,929,535 Parker Oct. 10, 1933 Y 2,052,818 Y Y Freyssinet et al Sept. 1, 1936 2,099,265 Freyssinet Nov. 16, 1937 2,101,015A Anderson Dec. 7, 1'937 2,152,738 Jeffery Apr. 4, 1939 2,253,792

Leavenworth Aug. 26. 1941 

